It all depends on what you want from archery. At your age there is no way I would limit myself to 45# if I was intending to hunt for the rest of my life. You may only be hunting whitetails now, but some time in your life you may have the opportunity to go after something bigger and tougher, and you will need more bow weight.
I'm almost 68 years old, 5'7", 154 lbs. My favorite bow is 55# at my 26 1/2 in. draw, and I don't see myself dropping more than a couple of pounds over the next 10 years. If you keep fit, do some toning exercises and stretches as you get older and continue to shoot your bows using good form and correct alignment there should be no reason to have fears about injuries from shooting a bow heavier than 45#.
Maybe a 45# bow is entirely adequate for most big game hunting, but with my meager 26 1/2" draw I feel that I need the extra cushion of an additional 8 to 10 pounds of draw weight - besides, I shoot 53-55# bows better than I do 45-48#.